Metal extraction without cyanide

Abstract

An improved process and composition for the extraction of metal from a metal-laden ore, soil or rock is provided. A liquid, three-component aqueous lixiviant comprises water, an alkali metal salt and a low pH acidic composition. A four-component aqueous lixiviant comprises water, a low pH acidic composition, an alkali metal salt and an acid having a pH value less than 2. Both lixiviant compositions are efficient for extracting metal into a pregnant liquid solution. The pregnant solution is treated by known conventional means, such as filtration, centrifuging or electrolysis to remove the extracted metals. The three-component and four-component aqueous lixiviants of the present invention are non-toxic, meaning, not an irritant or deleterious to humans or the environment and perform, as well as, or better than known toxic cyanide lixiviants. The aqueous lixiviants of the present invention effectively and efficiently extract gold, silver, platinum and other metals from ore laden soil or rock with efficiencies greater than 90%.

1. An improved process for the recovery of metal from a metal-containing ore, soil or rock, comprising the steps of:
 a) selecting a metal-containing ore; 
 b) crushing the metal-containing ore to form a powder; 
 c) conveying the powder to a mixing vat; 
 d) adding an amount of a three-component lixiviant that consists of:
 d-i) a liquid that is not an irritant or deleterious to humans and the environment, prepared by a process of combining a high purity acid selected from at least one of phosphoric acid, fumaric acid or acetic acid with water selected from at least one of deionized water and filtered water and an ammonium compound selected from at least one of anhydrous ammonia and buffered ammonium nitrate used in a ratio of approximately 1 lb, to approximately 5 lbs, of ammonium compound per gallon of water, heating the mixture to approximately 140° F. to form mixture (I), placing mixture (I) in a pressurized vessel and heating the mixture to temperatures in a range between approximately 250° F. and approximately 400° F., then cooling the mixture, after the mixture is cooled, adding a stabilizing amount of the starting mixture (I) forming a low pH acid (LpHAC) product that is not an irritant, 
 d-ii) a metal salt selected from at least one of potassium chloride, potassium sulfate, magnesium chloride, magnesium sulfate, calcium chloride, calcium sulfate, manganese chloride, manganese sulfate, sodium chloride, sodium sulfate, ammonium chloride, ammonium sulfate, ammonium bisulfate, and 
 d-iii) water selected from at least one of fresh water, sea water, brine, and a mixture thereof to form an aqueous metal extracting lixiviant; 
 
 e) forming a slurry of the metal containing ore powder and metal extracting lixiviant; 
 f) extracting metals from the slurry to form a pregnant liquid and a solid residue; 
 g) conveying the pregnant liquid and solid residue to a solid/liquid separator; 
 h) removing solids from the pregnant liquid and solid residue of step f); 
 i) directing the pregnant liquid of step g) to a metal recovery unit; and 
 j) collecting between approximately 85% to approximately 97% of total metal in the ore. 
 
     
     
       2. The process of  claim 1 , wherein the metal-containing ore contains at least one of copper, silver, gold, platinum, uranium, and rhodium. 
     
     
       3. The process of  claim 2 , wherein the metal-containing ore contains gold. 
     
     
       4. The process of  claim 2 , wherein the metal-containing ore contains copper. 
     
     
       5. The process of  claim 1 , wherein the metal salt is potassium chloride. 
     
     
       6. The process of  claim 1 , wherein the step of crushing the metal-containing ore by use of at least one of a rock crusher and a ball crusher. 
     
     
       7. The process of  claim 1 , wherein the step of collecting metal includes at least one of filtering, centrifuging, electrolysis, and fluid bed extractor. 
     
     
       8. The process of  claim 1 , wherein the ratio of three-component lixiviant to water in the aqueous slurry is in a range of from approximately 10% to approximately 90% lixiviant and approximately 90 weight % to approximately 10 weight % water. 
     
     
       9. The process of  claim 1 , wherein the metal recovery unit is selected from at least one of a centrifuge, electrolysis unit, molecular sieve, and fluid bed extractor. 
     
     
       10. The process of  claim 9 , wherein the metal recovery unit is an electrolysis unit. 
     
     
       11. A composition of matter that is a three-component lixiviant consisting of:
 a) a liquid that is not an irritant or deleterious to humans and the environment, prepared by a process of combining a high purity acid selected from at least one of phosphoric acid, fumaric acid or acetic acid with water selected from at least one of deionized water and filtered water and an ammonium compound selected from at least one of anhydrous ammonia and buffered ammonium nitrate used in a ratio of approximately 1 lb, to approximately 5 lbs, of ammonium compound per gallon of water, heating the mixture to approximately 140° F. to form mixture (I), placing mixture (I) in a pressurized vessel and heating the mixture to temperatures in a range between approximately 250° F. and approximately 400° F., then cooling the mixture, after the mixture is cooled, adding a stabilizing amount of the starting mixture (I) forming a low pH acid (LpHAC) product that is not an irritant, 
 b) an alkali metal salt selected from at least one of an alkali metal chloride and an alkali metal sulfate; and 
 c) water selected from at least one of fresh water, sea water, brine, and a mixture thereof to form an aqueous metal extracting lixiviant. 
 
     
     
       12. The composition of matter of  claim 11 , wherein the alkali metal chloride is potassium chloride. 
     
     
       13. An improved process for the recovery of metal from a metal-containing ore, soil or rock, comprising the steps of:
 a) selecting a metal-containing ore; 
 b) crushing the metal-containing ore to form a powder; 
 c) conveying the powder to a mixing vat; 
 d) adding an amount of a four-component aqueous lixiviant that consists essentially of
 d-i) water selected from at least one of fresh water, sea water, brine, and a mixture thereof, 
 d-ii) a liquid, non-irritant, low pH acidic composition (LpHAC) prepared by a process of combining a high purity acid selected from at least one of phosphoric acid, fumaric acid or acetic acid with water selected from at least one of deionized water and filtered water and an ammonium compound selected from at least one of anhydrous ammonia and buffered ammonium nitrate used in a ratio of approximately 1 lb. to approximately 5 lbs. of ammonium compound per gallon of water, heating the mixture to approximately 140° F. to form mixture (I), placing mixture (I) in a pressurized vessel and heating the mixture to temperatures in a range between approximately 250° F. and approximately 400° F., then cooling the mixture, after the mixture is cooled, adding a stabilizing amount of the starting mixture (I) forming a low pH acid (LpHAC) product that is not an irritant, 
 d-iii) an alkali metal salt selected from at least one of a alkali metal chloride and an alkali metal sulfate, and 
 d-iv) an acid having a pH of less than approximately 2, to form an aqueous metal extracting lixiviant; 
 
 e) forming a slurry of the metal containing ore powder and metal extracting lixiviant; 
 f) extracting metals from the slurry to form a pregnant liquid and a solid residue; 
 g) conveying the pregnant liquid and solid residue to a solid/liquid separator; 
 h) removing solids from the pregnant liquid and solid residue of step f); 
 i) directing the pregnant liquid of step g) to a metal recovery unit; and 
 j) collecting between approximately 85% to approximately 97% of total metal in the ore. 
 
     
     
       14. The process of  claim 13 , wherein the metal-containing ore contains at least one of copper, lead, molybdenum, cadmium, nickel, silver, cobalt, zinc, gold, platinum, uranium, rhodium, and aluminum. 
     
     
       15. The process of  claim 14 , wherein the metal-containing ore contains gold. 
     
     
       16. The process of  claim 14 , wherein the metal-containing ore contains copper. 
     
     
       17. The process of  claim 13 , wherein the alkali metal salt is potassium chloride. 
     
     
       18. The process of  claim 13 , wherein the acid with a pH of less than 2 is selected from at least one of nitric acid, hydrofluoric acid, hydrochloric acid, fumeric acid, and mixtures thereof. 
     
     
       19. The process of  claim 18 , wherein the acid with a pH of less than 2 is nitric acid.